1. Field of the Disclosure
Aspects relate to a scalable earliest arrival path (EAP) algorithm for simultaneous diversity transmissions of base station signals.
2. Description of the Related Art
Wireless communication systems have developed through various generations, including a first-generation analog wireless phone service (1G), a second-generation (2G) digital wireless phone service (including interim 2.5G networks) and third-generation (3G) and fourth-generation (4G) high speed data/Internet-capable wireless services. More recently, Long Term Evolution (LTE) has been developed by the 3rd Generation Partnership Project (3GPP) as a radio access network technology for wireless communication of high-speed data and packetized voice for mobile phones and other mobile terminals. LTE has evolved from the Global System for Mobile Communications (GSM) system and from derivatives of GSM, such as Enhanced Data rates for GSM Evolution (EDGE), Universal Mobile Telecommunications System (UMTS), and High-Speed Packet Access (HSPA).
To locate a wireless mobile device (referred to as a user equipment (UE) in LTE) geographically, there are several approaches. One is to use some form of terrestrial radio location based on measurements made by the wireless mobile device of signals transmitted by wireless network base stations and access points (APs) and/or based on measurements made by network elements (e.g., base stations and/or APs) of signals transmitted by the wireless mobile device. Another approach is to use a Global Positioning System (GPS) receiver or Global Navigation Satellite System (GNSS) receiver built into the wireless mobile device itself. Terrestrial radio location in a cellular telephony system may use measurements made by the wireless mobile device of transmission timing differences between pairs of base stations or APs and may employ trilateration or multilateration techniques to determine the position of the wireless mobile device based on two, or more commonly three or more, timing difference measurements.
One such terrestrial radio location method that is applicable to measurements of LTE base stations (referred to as eNodeBs or eNBs) and that is standardized by 3GPP in 3GPP Technical Specifications (TSs) 36.211, 36.305, and 36.355 is Observed Time Difference of Arrival (OTDOA). OTDOA is a multi-lateration method in which the wireless mobile device measures the time difference between specific Radio Frequency (RF) signals from several eNodeBs and either computes a location itself from these measurements or reports the measured time differences to a location server, such as an Enhanced Serving Mobile Location Center (E-SMLC) or a Secure User Plane Location (SUPL) Location Platform (SLP), which then computes the wireless mobile device's location. In either case, the measured time differences and knowledge of the eNodeBs' locations and relative transmission timing are used to calculate the wireless mobile device's position.
The same RF signal may take multiple paths from the signal source, e.g., an antenna of the eNodeB, to the receiver, e.g., an antenna of the wireless mobile device. Determining the Earliest Arrival Path (EAP), or the most direct RF signal from the signal source to the receiver, is an important function for accurately determining the position of the wireless mobile device using OTDOA. Current techniques for determining EAP, however, often fail to accurately identify the EAP.